Dual Chambers Promote Combustion Efficiency
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rLAIMED to combine the advantages N.-, of direct injection with the advantages of pre-combustion, a new dualchamber compression swirl combustion system was displayed by Ricardo and Co. Engineers (1927) Ltd. on an open day at the Shoreham-by-Sea laboratories of the company last week. Virtually identical chambers in the cylinder head and piston, having parallel offset axes. are each of two truncated sections joined by a cylindrical section, the injector being located at an angle of about 45° to the axis of the head chamber. The direction swirl is anti-clockwise in this chamber and clockwise in the piston chamber.
Thc interior surface of the chambers, therefore, comprises a series of flat planes which give improved scouring of the fuel by the swirling air compared with conventional pre-combustion chambers with curved surfaces. This reduces smoke emission, improves fuel consumption and power output and raises the b.m.e.p. It also facilitates operation of the engine at higher speeds.
In an application to a Berliet four cylinder with a bore of 120 mm. and stroke of 140 mm., the engine develops 100 b.h.p. at 2,300 r.p.m.. while maximum b.m.e.p. is 117 p.s.i. and 1,700 r.p.m The optimum fuel consumption of 0.4 lb. b.h.p./hr. is somewhat higher than that achieved with other test engines. Tho system can be applied as original equipment without difficulty and existing units are reasonably easy to convert, Investigations of heat flow from piston to coolant and of parasitic losses arising from pumping and mechanical friction are important aspects of tests being made to evaluate problems in the development of high-speed and highly turbocharged diesels. The tests show that increases in piston friction and pumping losses represent the main problem in the development of high-speed diesels.